Automatic switch for use in telephone or like systems



, Nov. 19, 1940.

R. TAYLOR ET AL 2,222,126

AUTOMATIC SWI TCH FOR USE IN TELEPHONE OR LIKE SYSTEMS Filed June 22,1938 IN VEN T0125 REGINALD TAYLOR GEOGE THOMAS BAKER Patented Nov. 19,1940 UNITED STATES PATENT OFFICE AUTOMATIC SWITCH FOR USE IN TELE- PHONEOR LIKE SYSTEMS Application June 22, 1938, Serial No. 215,032 In GreatBritain July 27, 1937 13 Claims.

The present invention relates to automatic switches for use in telephoneor like systems and is more particularly applicabletoelectromagnetically-operated step-by-step switches of the twomagnetvertical and rotary type which are arranged to have so-calledrectangular motion, that is to say, release is normally effected by theadvancement of the wipers beyond the end of the bank contacts afterwhich they fall and are then l0 rotated back to normal under the bank byspring tension.

Where such switches are required to absorb a digit, it has hitherto beenthe usual practice for the wipers to be set and to restore to normal inresponse to the digit in question and for release to be satisfactorilyeffected in the interdigital pause it has been found preferable toprovide arrangements whereby under this condition the wipers arerestored to normal along the path over which they were set. The use ofdifferent methods of release according to the circumstances involvesdifliculties unless an auxiliary release magnet is provided and this isnot altogether desirable since it renders switches of this type anon-standard item of manufacture. The chief object of the invention isto provide arrangements whereby on such switches the problems involvedin digit absorption may be satisfactorily solved.

According to one feature of the invention in a two-directionalelectromagnetically-operated step-by-step automatic switch provided withtwo sets of wipers the eifect of the absorption of the initial digittransmitted to the switch coupled with a wiper switching operation isobtained 5 without a release operation by arranging that alternateimpulses produce wiper switching and only alternate impulses efiectmovement of the wipers so that only the first half of the bank isaccessible in response to the first digit, only the second half of thebank being accessible in response to a further digit and only if thefirst digit is of such a value as to require absorption.

According to another feature of the invention in a two-directionalelectromagnetically-operated step-by-step automatic switch the primarymovement of the wipers is effected in response to alternate impulsesonly of the first digit, the circuit arrangements being such that if thedigit is of predetermined value the wipers are auto- 5 maticallyadvanced in the primary direction to a particular position from whichthey are again advanced in response to a further digit.

A further feature of the invention is that in a two-directionalelectromagnetically-operated step-by-step automatic switch of thevertical and rotary type provided with two sets of wipers alternatevimpulses only of the first digit effect vertical movement of the switchwipers and a wiper switching operation is also effected by alternateimpulses, the circuit arrangements being 5 such that if the first digitis of predetermined value the wipers are automatically given a furthervertical movement to a position representing a movement of half theheight of the bank from which they are again moved vertically inresponse 10 to alternate impulses of the succeeding digit.

The invention will be better understood from the following descriptionof one method of carrying it into effect, reference being had to theaccompanying drawing. This shows a circuit dia- 15 gram of adigit-absorbing group selector of the vertical and rotary type providedwith two sets of wipers each having access to one hundred outlets.

The circuit arrangements are such that each 20 alternate impulsereceived is absorbed, the vertical magnet and the wiper switching relayDA being operated on the. first and each subsequent odd impulse while oneach even impulse relay DA is released and the magnet is not operated.25 Hence one set of one hundred outlets may be accommodated on levels 1to 5, each of which has twenty outlets, ten upper and ten lower. Inresponse to digits of value 1 or 2, the switch wipers are raised tolevel 1 but in the former case access is had over operated armatures ofrelay DA to the upper set of outlets while in the latter case access ishad over resting armatures of relay DA to the lower set of outlets.Similar considerations apply to other pairs of odd and even digits. 35

If the wipers are raised by the first digit to an ordinary level, theswitch then performs a rotary hunting operation in a normal manner, thetesting taking place on either the upper or lower set of outletsaccording as to whether the digit is odd or even. If the wipers areraised to the predetermined digit-absorbing level, no cut-in takes placeand the switch hunts vertically to level 5 where it awaits the seconddigit which will in the manner already described carry the 4 wipers tothe desired set of outlets in the other. hundreds group situated onlevels 6 to 0.

Considering now the circuit operation, on the seizure of the switch froma preceding switch the loop extended across the incoming negative 50 andpositive conductors operates relay A which in, turn operates relay B.This relay locks over armature bl and at the same armature lights theswitch supervisory lamp LP. Relay B also at armature b2 operates relay Con its right-hand winding in series with resistance YB, at armature b1applies guarding earth to the incoming P conductor, and, assuming thatthe switch is functioning as a subscribers first selector, at armatureb6 connects up a dial tone transformer over common lead 12 to the middlewinding of relay A whereupon dial tone is extended by induction throughthe windings of this relay to the incoming speaking conductors in abalanced circuit. Relay C upon operating, at armature c4 prepares animpulsing circuit for the vertical magnet VM in series with its lowresistance left-hand winding, the magnet however being non-operative inseries with the winding of relay B.

On receipt of the first train of impulses relay A responds and on itsfirst de-energisation an energising circuit is completed for thevertical magnet VM as follows: earth, armatures bl and al, rotaryoff-normal contacts NR6, left-hand low resistance winding of relay C,armatures daZ and a l, rotary off-normal contacts NR4, magnet VM tobattery and accordingly the switch wipers are raised to level 1. Theoff-normal springs N are now mechanically operated and at contacts N3short-circuit the right-hand winding of relay C to enable it to holdoperated during the train. At contacts N4 an operating circuit iscompleted for relay H over its right-hand winding from earth, contactsNPBZ, armature c5, off-normal contacts N4 and armature b4 and this relaythereupon looks over its other winding to the earthed P conductor.

On the re-operation of relay A at the end of the first impulse, thevertical magnet remains held over the following circuit: earth,armatures bl and al, off-normal contacts N2, vertical magnet interruptercontacts um, armature ht, lefthand winding of relay DA to battery viathe vertical magnet. Relay DA now operates and at armature daZdisconnects the impulsing circuit to the magnet VM in readiness for theabsorption of the next pulse.

On the next release of relay A in response to the second impulse, thevertical magnet is released while relay DA now remains held over itsmiddle low resistance winding in series with the left-hand winding ofrelay C. At the end of the second impulse relay A re-operates andreleases relay DA since it will not hold operated in series with thecomparatively high resistance relay B.

Hence it will be seen that after the dialling of an odd digit thevertical magnet and relay DA will remain energised while after an evendigit they will both be released. During the impulse train relay B isintermittently short-circuited by armature al but it remains operateddue to the slugging effect of the short circuiting. The presence of themetal rectifier MBA in the energising circuit of relay B prevents theslowing up of the magnet operation which would otherwise result by thedirect connection of a comparatively low value non-inductive resistancein parallel with its winding. It will be readily understood that neitherthe magnet VM nor relay C will hold operated in series with relay B andmoreover the inductance of the latter relay is such that it has noappreciable effect on the magnet performance.

It will be assumed first that the wipers are raised to an ordinarylevel, that is, a level not set aside for digit absorption so that theswitch will function as an ordinary group selector.

At the end of the impulse train relay A remains operated and maintainsrelay B while after a circuit is completed from the earthed P lead tohold relay DA over its right-hand and middle windings in series if thetrain has comprised an odd number of impulses. The initial operatingcircuit for relay H is also disconnected and also its holding circuitover its left-hand winding but this relay now remains held on itsright-hand winding by way of armature b6, the rotary magnet interruptercontacts rm, armature h3 and the critical level normal post springcontacts NPAI. An energising circuit for the rotary magnet RM is alsocompleted from the same earth by way of off-normal contacts N4 andarmature c5 and the wipers are thereupon rotated into engagement withthe first set of contacts in the level selected, while the magnetinterrupter contacts T'ITL are opened. The rotary off-normal springs NRare mechanically operated on the first rotary step and at contacts NR5maintain the locking circuit for relay DA independently of armature cl,at contacts NR6 disconnect any impulsing circuit to relay C and atcontacts NR5 prevent the completion of any further circuit for themagnet VM over armature 04.

The switch now hunts for a free outlet in the level selected, accessbeing had over the negative 1, positive 1 and Pi wipers to the upper setof outlets on the level if an odd digit has been dialled and accessbeing had to the lower set of outlets if an even digit has been dialled.

If the first outlet encountered by the test wiper Pl or P2, as the casemay be, is engaged as indicated by the presence of earth or boosterbattery potential, relay 1-1 will be held operated over its left-handwinding and the disconnection of its right-hand winding by the contactsrm is therefore without effect. The rotary magnet deenergises howeverand on the closure of its interrupter contacts the magnet isre-energised to advance the wipers to the second set of contacts in thelevel selected. This stepping operation continues until an idle outletis reached or alternatively the wipers are advanced to the 11thposition.

If the test wiper encounters a free outlet, that is, one unmarked byearth or booster battery potential, relay I-I quickly restores and atarmature h3 further opens the magnet driving circuit while at armatureh2 it applies earth to the test wiper to guard the outlet seized. Acircuit is now completed to re-operate relay C over its right-handwinding by way of armatures hi and b2 since the short-circuiting earthhas already been removed therefrom at contacts NR3. Thereupon atarmature cl, c2 and 03 the incoming leads are extended through to thesucceeding switch, relay A is disconnected from the speaking leads andat the same time relay H is re-operated over its righthand winding.Relay A on releasing short-circuits relay B and during the release timeof the latter relay the loop extended forward over the negative andpositive wipers operates the A and B relays in the succeeding switchwhereupon a guard earth is returned over the test wiper so that whenrelay B subsequently restores relay H will be maintained on itsleft-hand winding and also relay DA on its right-hand and middlewindings in series if it has been operated.

In response to the dialling of subsequent digits trains of impulses aretransmitted straight through the switch to route the call to the wantedparty.

If all the outlets in the level selected prove busy, the wipers arerotated to the 11th position where the cam springs S are mechanicallyoperated. At contacts S3 the left-hand winding magnet as follows:

of relay H is disconnected from the test wiper so that on the opening ofthe interrupter contacts rm relay I-I releases as previously describedand opens the magnet driving circuit and reoperates relay C which inturn re-operates relay H. The incoming speaking leads are extended asbefore through to the wipers which however now connect by way of themultipled 11th step contacts back again to the upper and lower windingsof relay A which therefore remains held over the incoming loop andmaintains relay B. Contacts S2 disconnect the dial tone circuit and -atcontacts Si and S2 connect relay A in circuit with the busy flash andtone cam assemblies BF and BT over common leads l3 and II respectivelywhereupon busy tone and flash are applied to the incoming speaking leadsin well-known manner. Contacts S3 also extend earth over the test wiperto operate an overflow meter which may be connected to the 11th outletof that particular level for trailic observation purposes.

Considering now the case in which the first digit dialled raises theswitch wipers to the digit absorbing level, the normal post springs NPAare arranged to be mechanically operated by the switch shaft. If it isdesired that these springs shall be effective only on the odd digitcorresponding to this level, a strapping, shown bya circle and dashconnection, is taken from the contacts NPAI to armature dai so that incase the even digit is dialled the release of relay DA will shunt thecontacts NPAI to render them ineffective; similarly if the dottedconnection is utilised, the normal post springs will only becomeeffective as regards" the even digit.

On the release of relay C in the usual manner at the end of the impulsetrain, relay H releases since the holding earth is removed at the.operated contacts NPAI while for the same reason no energising circuitis completed for the rotary magnet RM. Relay H on releasing completes aself-interrupted driving circuit for the vertical earth, armatures bland al, oiT-normal contacts N2, vertical magnet interrupter contacts om,armatures 11.6 and c4, rotary off-normal contacts NR4, magnet VM tobattery and the switch wipers are accordingly raised verticallystep-by-step.

When the switch shaft reaches level 5, another set of normal postsprings NPB is operated and at contacts NPBi a circuit is completed byway of the protective resistance YA to maintain the vertical magnet inan energised condition while at contacts NPB3 the short-circuit isremoved from the right-hand winding of relay which now re-operates. Thisrelay releases relay DA at armature cl if it has already been operatedin response to the dialling of an odd digit and at armature c4 releasesthe vertical magnet and again connects it to the iinpulsing circuit inreadiness for the second train of impulses which will follow at theconclusion of the interdigital pause.

By the above arrangement the time available even in the shortestinterdigital pause is ample for the purpose of digit absorption,particularly since digit 7 is usually allocated as the digit to beabsorbed so that the switch will have to make one step only to reachlevel 5 in readiness for the next digit.

On the dialling of the second digit the switch steps vertically fromlevel 5 and in the manner previously described each alternate impulse isabsorbed. The switch then performs an automatic rotary search for a freeoutlet in the selected group of outlets.

When the connection is released at the conclusion of the conversation,earth is removed from the P conductor at the controlling switch in thetrain thereby releasing relay H and also relay DA if it has beenoperated. Relay H disconnects the holding circuit for relay C whichpreviously existed over armatures c6 and h! and on the release of relayC a self-interrupted driving circuit is completed for the rotary magnetRM from earth supplied to common conductor Iii by way of delayed alarmequipment, armatures b3 and h3, interrupted contacts rm, off-normalcontacts N4, armature c5 and magnet RM to battery. Accordingly thewipers are rotated clear of the banks after which they fall and rotateby spring tension back to their normal position where the off-normalcontacts N4 open and disconnect the release circuit.

At the commencement of release an unguard period on the incoming Pconductor which is represented by the sum of the release times of relaysH and C is provided to enable preceding switches to restore. On therelease of relay C following the release of relay H earth is replaced onthe P conductor over armature c6 and ofi-norrnal contacts NI until theswitch has completely restored to normal when the earth is removed bythe opening of the off-normal contacts NI We claim:

1. In a telephone system, an automatic switch having a plurality of setsof wipers and corresponding groups of contacts, means in the switchresponsive to received impulses for alternately operating the sets ofwipers and switching from one set to another, said means operated inresponse to a first digit to select a contact only in a portion of thecontacts of each group, the contacts in another portion of each groupbeing se-' lectable only when the switch is operated in response to morethan one digit.

2. A telephone system as claimed in claim 1, wherein the contacts in theother portion of each group are selected only when a particular firstdigit is received by said switch.

3. In a telephone system, an automatic switch having a plurality of setsof wipers and means responsive only to alternate received impulses of afirst digit for moving the wipers, means responsive to the receipt of aparticular digit to automatically move the wipers to a particularposition, and means responsive to a further digit for further movingsaid wipers.

4. An automatic switch of the two directional type having a plurality ofsets of wipers, a bank of contacts for each set, means responsive toalternate received impulses for alternately operating the wipersvertically and switching from one wiper set to another, means in theswitch operated responsive to received impulses corresponding to aparticular digit for automatically oper-. ating the sets of wipersvertically past one group of contacts in each bank, said first meansthereafter responsive to a succeeding digit to operate the wipersvertically only by each alternate impulse thereof.

5. An automatic switch as claimed in claim 4 wherein said first means isalso responsive to each alternate impulse of a succeeding digit toswitch from one set of wipers to another.

6. In a telephone system, an automatic switch having vertical and rotarymovement, a pair of wiper sets therefor, a bank of contacts for eachwiper set, means in said switch responsive to a first digit to select acontact in only the first half of each bank of contacts, said meansresponsive to a particular first digit to prepare for selection ofcontacts in the second half of each bank of contacts and thereafterresponsive to a second digit delivered to the switch to select anycontact set in only the second half of each bank of contacts.

7 In a telephone system, an automatic switch having vertical and rotarymovement and a plurality of sets of wipers and contacts for each setarranged in levels, a vertical magnet and a switching relay in theswitch, means in said switch responsive to alternate impulses of a firstdigit received by said switch to operate the vertical magnet to raisethe wipers and to alternate impulses to switch from one set of wipers toanother to select contacts only in particular levels, means in theswitch responsive to a particular first digit received thereby to causethe wiper sets to prepare the switch for selection of contacts only inanother group of levels, said first means responsive only to a seconddigit to select a set of contacts in said other group by means of eitherset of wipers.

8. In a telephone system, an automatic switch having vertical and rotarymovement and having a plurality of wiper sets each having access to abank of contacts, means in the switch responsive to a first digitreceived by the switch for selecting a line in only a portion of thebanks accessible to each wiper, means responsive to a particular firstdigit for preparing the switch to select contacts in another portion ofthe banks,

for switching from one set of wipers to the other,

means in the switch responsive to the receipt of one impulse of a digitreceived by said switch to operate both the magnet and the relay, andmeans responsive to the next impulse of the digit to deenergize both therelay and magnet.

11. A telephone system as claimed in claim 10 wherein the relay andmagnet are thus operated by a first digit to select trunks in one groupand are similarly operated in one instance by a second digit to selecttrunks in a second group.

12. In a telephone system an automatic switch having vertical and rotarymovement and having a plurality of sets of wipers, a vertical magnet inthe switch for operating said wipers, a relay in the switch forswitching wipers, means in the switch responsive to impulses of areceived digit to operate the magnet and relay in response to oddnumbered impulses and responsive to even numbered impulses to causedeenergization of both, whereby a line may be selected over any wiperset.

13. A telephone system as claimed in claim 12,

wherein there are two groups of lines accessible to each wiper set andmeans for absorbing a particular first digit to cause odd and evenimpulses of a subsequently received digit to select a line in a secondof said groups only.

REGINALD TAYLOR. GEORGE THOMAS BAKER.

